Modular seabed processing system

ABSTRACT

To install a modular seabed processing system ( 1 ) on a seabed, a monopile foundation ( 3 ) is first lowered down and driven in to the seabed. A docking unit ( 4 ) is lowered towards the installed foundation ( 3 ) so that a mating clamp system ( 6 ) mounted on the docking unit is aligned with a spigot ( 5 ) on the foundation. The clamp system then clamps the spigot to fix the docking unit onto the foundation. Flowlines ( 2 ) and an electrical power connector plug ( 18 ) are connected to the docking unit. A first retrievable substantially autonomous module ( 8 ) is lowered and connected to the docking unit (4) by a multi-bored connector ( 10, 11 ) and the plug ( 18 ) on the docking unit is engaged by a corresponding socket ( 17 ) on the module. Isolation valves ( 14, 16 ) in the docking unit and module are opened so that the module ( 8 ) is able to act on fluid received from the flowlines ( 2 ) via the multi-bored connector ( 10, 11 ). A second retrievable substantially autonomous module is also connected to the docking unit ( 4 ) in the same way.

[0001] The present invention relates to a system suitable for exploitingoil/gas fields and, more particularly, subsea fields and a method ofinstalling such a system.

[0002] Conventional oil/gas fields have a plurality of wells linked to ahost facility which receives the oil/gas via flow lines. A conventionalunderwater oil/gas field may include modularised processing systemsbetween the wells and the host facility.

[0003] GB 2261271 describes a modularised processing system which isused to separate a mixture of oil, gas and water from wells into itsindividual components. The system comprises an offshore installation inwhich interchangeable modules are individually supported in a supportframework located on the seabed, the modules being used to separate themixture. Two-part connectors enable modules to be lowered from thesurface of the sea into the framework and be connected up to the wells.The modules can also be retrieved from the system so that maintenancecan be carried out on them when they are out of the water.

[0004] Such a framework is a large, heavy structure which requiresexpensive guidance means for guiding the modules into the framework.

[0005] It is therefore an object of the present invention to provide animproved system for such modules and a method of installation of such asystem.

[0006] According to one aspect of the present invention there isprovided a method of installing a system, comprising the steps of:

[0007] installing a foundation into ground;

[0008] fixing a docking unit to the foundation via a single connection;

[0009] connecting flowlines to the docking unit; and connecting at leastone retrievable substantially autonomous module to the docking unit sothat the or each module is able to act on fluid received from theflowlines.

[0010] By having a single connection between the docking unit and thefoundation, the installation of the docking unit is made far simpler.The single connection may comprise a connection of a type used for awell head.

[0011] The step of fixing the docking unit to the foundation via asingle connection may comprise clamping a mating clamp arrangementattached to one of the docking unit or the foundation to a protrusionattached to the other of the docking unit or foundation. The protrusionis preferably substantially centrally placed on the docking unit orfoundation.

[0012] The step of connecting at least one retrievable substantiallyautonomous module to the docking unit desirably includes actuatingisolation means to connect at least one module to the flowlines, theisolation means comprising a first portion in the module and acomplementary second portion in the docking unit.

[0013] The method may include an uninstalling step of disconnecting onesaid retrievable substantially autonomous module from the docking unit,without affecting the operation of any other retrievable substantiallyautonomous module with the flowlines and without effecting theconnection of any other such module. The uninstalling step desirablyincludes actuating the isolation means to isolate the module beingdisconnected from the docking unit and the flowlines connected thereto.

[0014] The isolation means may comprise an isolation connector of a typeused for a well head. The isolation means may comprise a multi-portedvalve isolation connector.

[0015] It may be desirable for the method to include the steps ofconnecting a first portion of a power connector to the docking unit, thefirst portion of the power connector being connected to a power sourceremote from the docking unit, and connecting a complementary secondportion of the power connector in one said retrievable substantiallyautonomous module to the first portion so that the power source is ableto provide power to the module. The power connector may be adapted tocarry control signals to or from the module.

[0016] The step of connecting at least one retrievable substantiallyautonomous module to the docking unit may include providing guidingmeans to guide said module into connection with the docking unit. Theguiding means desirably ensures that the second portion of the powerconnector of the module engages the first portion of the power connectoron the docking unit.

[0017] The ground is preferably a seabed. The foundation may comprise asingle pile.

[0018] According to another aspect of the present invention there isprovided a system comprising:

[0019] a foundation installed into ground;

[0020] a docking unit fixed to the foundation via a single connection;and

[0021] at least one retrievable substantially autonomous module, the oreach module being connected to the docking unit so that the or eachmodule is able to act on fluid received from the flowlines.

[0022] The system has a much smaller “footprint” on, say, a seabed, andis also lighter and cheaper than a system having a support framework forinterchangeable modules.

[0023] Embodiments of the present invention will now be described, byway of example, with reference to the accompanying drawings, in which:—

[0024]FIGS. 1 and 2 are side elevations of a system, according to oneembodiment of the invention;

[0025] FIGS. 3 to 17 are side elevations showing the installation of thesystem; and

[0026] FIGS. 18 to 23 are side elevations showing modifications to thefoundations for the system.

[0027] Referring to FIGS. 1 and 2 of the accompanying drawings, amodular seabed processing system 1 is illustrated which is connected byunderwater flowlines 2 to wells (not shown) which remove a fluid mixturecomprising water and oil/gas from reservoirs beneath the seabed. Thesystem comprises a monopile foundation 3 to which a docking unit ormanifold 4 is connected. A spigot 5 (see FIG. 3) projects upwardly fromthe centre of the head of the pile 3 and is clamped by a mating clampsystem 6 mounted to the base of the docking unit 4. The spigot 5 is anintegral part of the pile 3.

[0028] The flowlines 2 from the wells are connected to the docking unit4 and pipelines or flowlines 7 connect the docking unit 4 to a hostfacility (not shown). The host facility may be, for example, onshore oron a fixed or a floating rig.

[0029] Also connected to the docking unit 4 is a pair of retrievablesubstantially autonomous modules 8,9. Each module 8,9 has a firstportion 10 of a multi-bored connector (see also FIGS. 12 and 13) at itsbase which is connected to a complementary second portion 11 of themulti-bored connector (see also FIGS. 6 and 7) mounted on top of thedocking unit 4, each multi-bored connector has a guidance cone 12surrounding it for alignment purposes when a module is installed on thedocking unit. Pipework 13 is provided within the docking unit 4 toconnect the flowlines 2 and the pipelines 7 to the second portion 11 ofthe multi-bored connector. The pipework has isolation valves 14.

[0030] Each retrievable substantially autonomous module 8,9 has aseparator chamber 15 for separating fluids from the fluid mixture. Theseparator chamber 15 is connected to the first portion 10 of themulti-bored connector via isolation valves 16.

[0031] Each module 8,9 has an electric power connector socket 17 engagedwith a corresponding plug 18 attached to the docking unit 4. Each plug18 is connected to an integrated umbilical 19 from the host facility.The umbilicals 19 are adapted to provide power, control signals andchemical injection from the host facility to the modules 8,9. Thecontrol signals are sent to control, reprogramme or shut down themodules 8,9 which are otherwise self-controlling during normal running.The chemicals are injected into the modules 8,9 as part of their normaloperation or as a result of a planned or unplanned shut down to preventunwanted chemical reactions such as hydrate formation, wax depositionand corrosion. Each module 8,9 also has stab connectors (not shown) forconnecting to corresponding stab connectors (not shown) on the dockingunit 4 so that the module is able to receive the chemical injection.

[0032] Referring to FIGS. 3 to 17, the process of installation of thesystem on a seabed will now be described.

[0033] The monopile foundation 3 is lowered down to the seabed anddriven into the seabed in a conventional manner. FIG. 3 shows itinstalled.

[0034] The isolation valves 14 in the pipework 13 in the docking unit 4are set to closed positions.

[0035] [FIGS. 4 and 5] The docking unit 4 is placed in installationrigging 20 which is lowered from a surface vessel towards the monopilefoundation 3.

[0036] [FIGS. 6 and 7] The mating clamp system 6 mounted on the base ofthe docking unit is approximately aligned with the spigot 5, the matingclamp system being then remotely activated by, say, a remotely operatedvehicle (ROV), so as to clamp the spigot, fixing the docking unit 4 tothe monopile foundation 3.

[0037] [FIGS. 8 and 9] Pipeline connectors 21 at the end of thepipelines 7 from the host facility are connected to the docking unit 4and flowline connectors 22 at the end of flowlines 2 from the wellheadsare connected to the docking unit in a conventional manner by, say, ROVsor remotely operated tools (ROTs).

[0038] [FIGS. 10 and 11] The electrical power connector plug 18 at theend of the umbilical 19 from the host facility is attached to thedocking unit 4 in a conventional manner by being lowered from thesurface vessel.

[0039] Before a first retrievable substantially autonomous module 8 islowered from, for example, the surface vessel towards the docking unit4, the module isolation valves 16 are set to closed positions. Systemsin the module 8 are rigorously tested before the module is lowered.

[0040] [FIGS. 12 and 13] The first retrievable substantially autonomousmodule 8 is then lowered towards the docking unit 4.

[0041] The first portion 10 of the multi-bored connector at the base ofthe module 8 is approximately aligned with one of the guidance cones 12on the docking unit 4. The cone 12 guides the first portion 10 intospecific alignment with the complementary second portion 11 of themulti-bored connector.

[0042] [FIGS. 14 and 15] When the first and second portions 10,11 of themulti-bored connector 11 are correctly aligned, this causes theelectrical power connector socket 17 of the module 8 to be specificallyaligned with a corresponding electrical power connector plug 18 on thedocking unit 4. Thus, the two portions 10,11 of the multi-boredconnector engage and the plug 18 and socket 17 engage.

[0043] [FIGS. 16 and 17] A second retrievable autonomous module 9 islowered and installed on the docking unit 4 in the same way.

[0044] Referring back to FIGS. 1 and 2, in use, the docking unitisolation valves 14 and the module isolation valves 16 are opened. Fluidmixture from the wells is received into the module separator chambers 15via the flowlines 2 and the open isolation valves 14,16. The fluidmixture is separated into gas and liquid by the module separatorchambers 15. The separated gas and liquid are then transported by thepipelines 7 to the host facility.

[0045] To retrieve one of the modules from the seabed processing system1, that module 8 needs to be uninstalled. The module 8 to bedisconnected is isolated from the rest of the seabed processing system 1by closing the isolation valves 14 in the pipework 13 to the secondportion of the multi-bored connector 11 for that module 8 and theisolation valves 16 in that module. The module 8 is then retrievedwithout affecting the connection of the other module 9 in the system.Hence, the production operation of the other module 9 is not disturbed.Thus, a module may be easily retrieved for maintenance/repair purposes.

[0046] A module may be retrieved so that it can be reconfigured foranother use. A module may not have a separator chamber but may, forexample, be configured to simply manifold or pump fluid mixture receivedfrom the connected wells.

[0047] In a modification shown in FIGS. 18 and 19, the monopilefoundation has been replaced by a caisson pile base foundation whichalso has a centrally placed spigot 5, projecting upwardly from the headof the foundation, for being clamped by the mating clamp system 6 at thebase of the docking unit 4 when it is lowered onto it by an installationframe 20.

[0048] In another modification shown in FIGS. 20 and 21, the monopilefoundation has been replaced by a suction base foundation 25. Thiscomprises a number of compartments 26 attached to the underside of aframework 27, wherein water is pumped out of the compartments to drawthem into the seabed. The framework 27 has a centrally placed spigot 5projecting upwardly therefrom. This spigot 5 is also adapted to beingclamped by the mating clamp system 6 at the base of the docking unit 4when it is lowered onto it by an installation frame 20.

[0049] In yet another modification shown in FIGS. 22 and 23, themonopile foundation has been replaced by a mechanically locked pilefoundation 29. This comprises a number of piles 30 installed in theseabed with a framework 31 surrounding the top portion of the piles. Thepiles 30 are then mechanically locked to the framework 31, such as byexpanding the outer tube of each pile 30 so that it forcefully engagesthe surrounding framework 31. The framework 31 has a centrally placedspigot 5 projecting upwardly therefrom which is adapted to be clamped bythe mating clamp 6 system at the base of the docking unit 4 when it islowered onto it by an installation frame 20.

[0050] A system according to the invention is capable of operating atlarge “step-out” distances such as over 50 Km from a host facility andin deep water. Therefore, less host facilities are required to exploit aparticular field and the life of a host facility can be extended byconnecting it to remote satellite fields. Furthermore the system permitsabandoned fields to be reopened and marginal fields to be exploited.

[0051] The system may use connecting means used for a well head forconnecting the docking unit 4 to the foundation 3. The multi-boredconnector 10, 11 may comprise other connecting means used for a wellhead. The multibored connector may be a multi-bored valve isolationconnector, such as the one described in GB 2261.271.

[0052] Whilst a particular embodiment has been described, it will beunderstood that various modifications may be made without departing fromthe scope of the invention. For example, any suitable number of seabedprocessing systems may be used in a field.

[0053] The docking unit may be designed to hold any suitable number ofretrievable substantially autonomous modules.

[0054] The pipelines between the seabed processing systems and the hostfacility may carry any suitable component separated from the fluidmixture extracted by wells.

[0055] The integrated umbilical may be replaced with separate power,control signal and chemical injection lines. Separate power and controlsignal lines may be replaced by an integrated power/control line.

[0056] The system may be land-based and not underwater.

1. A method of installing a system (1), comprising the steps of:installing a foundation (3) into ground; fixing a docking unit (4) tothe foundation via a single connection (5,6); connecting at least oneflowline (2) to the docking unit; and connecting at least oneretrievable substantially autonomous module (8,9) to the docking unit sothat the or each module is able to act on fluid received from the oreach flowline.
 2. A method as claimed in claim 1, wherein the step offixing the docking unit (4) to the foundation (3) via a singleconnection (5,6) comprises clamping a mating clamp arrangement (6)attached to one of the docking unit or the foundation to a protrusion(5) attached to the other of the docking unit or foundation.
 3. A methodas claimed in claim 1 or 2, wherein the step of connecting at least oneretrievable substantially autonomous module (8,9) to the docking unit(4) includes actuating isolation means (10,11) to connect at least onemodule to said at least one flowline (2), the isolation means comprisinga first portion (10) in the module and a complementary second portion(11) in the docking unit.
 4. A method as claimed in claim 1, 2 or 3,including an uninstalling step of disconnecting one said retrievablesubstantially autonomous module (8) from the docking unit (4), withoutaffecting the operation of any other retrievable substantiallyautonomous module (9) and without effecting the connection of any othersuch module (9) with said at least one flowline (2).
 5. A method asclaimed in claims 3 and 4, wherein the uninstalling step includesactuating the isolation means (10,11) to isolate the module (8) beingdisconnected from the docking unit (4) and said at least one flowline(2) connected thereto.
 6. A method as claimed in any preceding claim,including the steps of connecting a first portion (18) of a powerconnector (17,18) to the docking unit (4), the first portion of thepower connector being connected to a power source remote from thedocking unit, and connecting a complementary second portion (17) of thepower connector comprising part of one said retrievable substantiallyautonomous module (8) to the first portion (18) so that the power sourceis able to provide power to the module.
 7. A method as claimed in anypreceding claim, wherein the step of connecting at least one retrievablesubstantially autonomous module (8,9) to the docking unit (4) includesproviding guiding means (12) to guide said at least one module intoconnection with the docking unit.
 8. A method as claimed in claims 6 and7, wherein the guiding means (12) ensures that the second portion (17)of the power connector engages the first portion (18) of the powerconnector.
 9. A method as claimed in any preceding claim, including thestep of connecting at least one outlet flowline (7) to the docking unit(4) for receiving fluid acted upon by said at least one module (8,9).10. A method as claimed in claim 2 or any claim dependent thereon,wherein the protrusion (5) is substantially centrally placed on thedocking unit (4) or foundation (3).
 11. A method as claimed in claim 6or any claim dependent thereon, wherein the power connector is adaptedto carry control signals to or from the module.
 12. A method as claimedin any preceding claim, wherein the single connection (5,6) comprises aconnection of a type used for a well head.
 13. A method as claimed inclaim 3 or any claim dependent thereon, wherein the isolation means(10,11) comprises an isolation connector of a type used for a well head.14. A method as claimed in claim 3 or any claim dependent thereon,wherein the isolation means (10,11) comprises a multi-ported valveisolation connector.
 15. A method as claimed in any preceding claim,wherein the foundation (3) comprises a single pile.
 16. A method asclaimed in any preceding claim, wherein the ground is a seabed.
 17. Asystem (1) comprising: a foundation (3) installed into ground; a dockingunit (4) fixed to the foundation via a single connection (5,6); and atleast one retrievable substantially autonomous module (8), the or eachmodule being connected to the docking unit so that the or each module isable to act on fluid received from at least one flowline (2) when saidat least one flowline is connected to the docking unit (4).
 18. A systemas claimed in claim 17, wherein the single connection comprises a matingclamp arrangement (6) attached to one of the docking unit (4) or thefoundation (3) clamped to a protrusion (5) attached to the other of thedocking unit or foundation.
 19. A system as claimed in claim 17 or 18,including isolation means comprising a first portion (10) in one saidmodule (8,9) and a complementary second portion (11) in the docking unit(4), the isolation means adapted to be actuated to connect one saidmodule to said at least one flowline (2).
 20. A system as claimed inclaim 17, 18 or 19, including a power connector comprisinginterconnectable first and second portions, the first portion (18) beingconnected to the docking unit (4), and the second portion (17)comprising part of one said retrievable substantially autonomous module(8,9).
 21. A system as claimed in claim 20, wherein the power connector(18,17) is adapted to carry control signals to or from the module (8,9).22. A system as claimed in any one of claims 17 to 21, including guidingmeans (12) for guiding said at least one module into connection with thedocking unit (4).
 23. A system as claimed in claim 20 and 22, whereinthe guiding means (12) is adapted to enable the first and secondportions (18,17) of the power connector to engage.
 24. A system asclaimed in claim 18 or any claim dependent thereon, wherein theprotrusion (5) is substantially centrally placed on the docking unit (4)or foundation (3).
 25. A system as claimed in any one of claims 17 to24, wherein the single connection (5,6) comprises a connection of a typeused for a well head.
 26. A system as claimed in claim 19 or any claimdependent thereon, wherein the isolation means (10,1 1) comprises anisolation connector of a type used for a well head.
 27. A system asclaimed in claim 19 or any claim dependent thereon, wherein theisolation means (10,11) comprises a multi-ported valve isolationconnector.
 28. A system as claimed in any one of claims 17 to 27,wherein the foundation (3) comprises a single pile.